A general strategy for all-solid-state batteries with agglomeration-free and high conductivity achieved by improving the interface compatibility of fillers and polymer matrix

Composite solid electrolytes (CSEs) composed of polymer matrix and inorganic fillers show considerable potential for applications in all-solid-state lithium (Li) metal batteries. However, challenges such as fillers agglomeration and low lithium ion transference number (tLi+) remain significant obstacles to the practical application of CSEs. Herein, a general strategy of graft polymerization on the fillers surface to modulate the interface compatibility with the polymer matrix is proposed, and CSEs are prepared to verify the feasibility. The microstructure and composition of the surface coating of the fillers are analyzed, with subsequent studies of the fillers distribution within the CSEs confirming the improved interface compatibility. The enhancement of interface compatibility facilitates uniform dispersion of fillers, thereby greatly improving the utilization of fillers. CSEs exhibits high ionic conductivity (0.163 mS·cm−1 at 30 °C) and tLi+ (0.77), which gives the battery excellent rate performance and cycle stability. Therefore, chemical grafting of polymer onto the fillers surface to enhance the interface compatibility with the polymer matrix represents a promising strategy for the practical application of solid-state batteries.